Abstract

Jacqueline Krim
Robert P. Berhinger
Physics Department
Duke University
Note: JK was on leave from North Carolina State University while the research was performed and the article was written and published.

Theorists have always believed that friction plays a great role in avalanche-like collapse of a granular piles, but the predictions have proven difficult to test experimentally. We devised an experimentally controlled way to demonstrate the impact of friction, accessible to all who dare try.[1-3] With the aid of a middle school assistant, we studied and filmed piles of apples, oranges, and onions as one or more pieces of fruit were removed. Among other things, we discovered that increasing the friction of the onions (by peeling them) vastly decreased the likelihood of collapse. Our work includes videos written by, produced, and starring our 7th grade assistant, some of which are posted on the Physics Today YouTube channel.[2]